1. Field
This invention relates to all processes which include the requirement that two, or more liquids are mixed thoroughly and then separated. The liquids are immiscible. The more polar of the liquids is dispersed in another liquid as the continuous phase of the mixture. The invention, then specifically relates to the application of an electrostatic field generated to vary in gradient along the flow path of the mixture to first mix the fluids and then coalsesce the dispersed drops of the more polar fluid.
2. The State of the Art
In the oil field, the dispersion of water droplets in oil is well-known. The dispersion may form a very "tight" emulsion, an emulsion which is very stable, i.e., will not break down with time. Whether the emulsion is formed naturally, and is so produced, or whether it is created by liquid-shearing pumps, the separation is a well developed art.
Several forces have been used to demulsify oil and water. When water is removed from oil, the oil is sometimes referred to as "dehydrated" rather than demulsified. It does not matter, at this level of description--the water is removed from the oil and an entire industry has developed to achieve this result and so reduce the cost of transporting and refining the produced petroleum. Among the forces brought to bear is that of the electrostatic field generated by electrodes energized by a source of electrical energy. In the field, a dispersed, more polar, fluid will have its droplets moved into collison with each other, the collison will cause little droplets to form big drops. Gravity will take over and the large drops will move from their surrounding continuous phase of fluid and separate.
Some of the history of the electrostatic field in the petroleum industry is found in recently issued U.S. Pat. No. 4,039,404. This disclosure is incorporated by reference for the purpose of background. A more fundamental tracing of this use of the electrostatic field is found in U.S. Pat. No. 3,772,180 which is incorporated into this application with the pride of authorship.
The petroleum fluids are not the only fluids with the problem of separation after two of the fluids have been mixed. For years, the mining industry has been developing the technology of leaching metals from ore with acid and transferring the metallic cations to liquids from which the metal can be commercially extracted.
A specific example of this mining technique is the selective recovery of copper from aqueous solutions resulting from leaching copper-bearing minerals. Organic, water-immiscible extracting agents are intimately contacted with the aqueous, copper-bearing solution, resulting in a transfer of the copper values from the aqueous phase to the organic phase. The phases have previously been allowed to separate in large settling tanks, and the copper recovered from the separated organic phase. The output of these processes has been limited by the size of the settling tanks, sufficient residency in the settling tanks being required to obtain satisfactory separation of the organic phase and the aqueous phase.
In a United Kingdom Pat. No. 909,485, processes are disclosed wherein an aqueous phase and an organic phase are first intimately mixed with each other, the dispersion or mixture being subsequently separated into its respective phases in a gravity settling tank. Improved settling rates were obtained by producing a high voltage electric field in the settling tank in the region of the emulsion and separating the aqueous phase from the organic phase.
Describing other industries where fluids must be separated from fluids can be done, however, more examples might form a patchwork in which the basic problem might be obscured, there is a problem of mixing the fluids, for whatever processing purpose will be served. Then there is the separation problem. The mixing problem revolves around bringing the fluids together to transfer material between them but avoiding formation of an emulsion of the fluids which is so tight that separation takes so long that the size of the inventory of fluids gets out of hand. Further, if mechanical mixing apparatus can be eliminated, capital and maintenance costs can be reduced. Seeking this goal, the use of the electrostatic field to both mix and then separate the fluids is an intriguing advance in the art.